Swedish scientist Hannes Alfvén is considered a founding father of the field of plasma physics. He made important contributions to interplanetary physics, magnetospheric physics, the method for calculating particle orbits, and the modern understanding of comet tails, frozen-in magnetic flux, the magnetosphere (protective plasma covering the earth), plasma dynamics, the solar system, and the nature of the universe. For decades, several of his most important ideas were widely considered bunk, but these theories have gradually been proven by advancing technologies of the 1970s and '80s.

In 1937 he proposed the existence of a galactic magnetic field, with cosmic rays moving in spiral orbits within our galaxy, driven by the magnetic field. Though doubted by leading experts of the time, this was generally confirmed by satellite observation in 1973.

In 1939 he proposed a theory explaining magnetic storms and auroras, using the spiraling electric charges within magnetic fields to calculate how electrons and ions move. His paper was rejected for publication in the leading scientific journal Terrestrial Magnetism and Atmospheric Electricity, and was instead published in an obscure Swedish-language journal, but Alfvén's explanation came to be considered plausible by the 1960s, and was widely accepted by the 1970s.

In 1942 he explained the magnetohydrodynamic wave, a hydromagnetic shear wave in a charged plasma, now also called the Alfvén wave. This breakthrough too was almost universally ignored, until six years later when he delivered a lecture at the University of Chicago with Enrico Fermi in the audience, and Fermi interrupted the presentation by saying "Of course" and nodding his head yes.

In 1950 he identified non-thermal radiation from astronomical sources as synchrotron radiation, left by electrons in the presence of magnetic fields. In 1963 he hypothesized a large-scale filamentary structure of the universe, which put him somewhat at odds with the consensus acceptance of Big Bang cosmology. His concept of symmetric cosmology, which posits that the universe consists of matter and anti-matter in equal quantities separated only by thin boundary layers, remains controversial. Alfvén won the Nobel Prize for Physics in 1970, sharing the honor and stipend with French physicist Louis Néel, and he is the namesake of the Alfvén Medal of the European Geophysical Union.

In the latter decades of his career, Alfvén split his time between California and Sweden, spending October to March at the University of California at San Diego and April to September at the KTH Royal Institute of Technology in Stockholm. He also authored several books explaining science to a non-expert audience, including a 1968 book written under the pen name Olof Johannesson explaining the dangers of super-computers. He formally retired in 1973, but until his death in 1995 he never went more than a few days without appearing at one of his workplaces.

His uncle, Hugo Emil Alfvén (1872-1960) was a prominent Swedish composer and violinist, best known for his Midsommarvaka (Midsummer Vigil), also called Swedish Rhapsody No. 1, a piece which remains popular in symphonic performances to this day.

Author of books:Cosmical Electrodynamics (1950)On the Origin of the Solar System (1954)Worlds-Antiworlds: Antimatter in Cosmology (1966)The Great Computer: A Vision (1968, as Olof Johannesson)Atom, Man, and the Universe: A Long Chain of Complications (1969)Living on the Third Planet (1972)Structure and Evolutionary History of the Solar System (1975, with Gustaf Arrhenius)Cosmic Plasma (1981)